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Ann. Geophys., 24, 861-872, 2006
www.ann-geophys.net/24/861/2006/
© European Geosciences Union 2006
Precipitation and total power consumption in the ionosphere: Global MHD simulation results compared with Polar and SNOE observations
M. Palmroth1, P. Janhunen1,2, G. Germany3, D. Lummerzheim4, K. Liou5, D. N. Baker6, C. Barth6, A. T. Weatherwax7, and J. Watermann8
1Space Research Division, Finnish Meteorological Institute, Helsinki, Finland
2Department of Physical Sciences, University of Helsinki, Helsinki, Finland
3University of Alabama in Huntsville, Huntsville, AL, USA
4Geophysical Institute, University of Alaska, Fairbanks, AK, USA
5Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD, USA
6Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO, USA
7Siena College, Department of Physics, Loudonville, NY, USA
8Danish Meteorological Institute, Atmosphere Space Research Division, Farum, Denmark
Abstract. We compare the ionospheric electron precipitation morphology and power from a
global MHD simulation (GUMICS-4) with direct measurements of auroral energy
flux during a pair of substorms on 28-29 March 1998. The electron
precipitation power is computed directly from global images of auroral light
observed by the Polar satellite ultraviolet imager (UVI). Independent of the
Polar UVI measurements, the electron precipitation energy is determined from
SNOE satellite observations on the thermospheric nitric oxide (NO) density.
We find that the GUMICS-4 simulation reproduces the spatial variation of the
global aurora rather reliably in the sense that the onset of the substorm is
shown in GUMICS-4 simulation as enhanced precipitation in the right location
at the right time. The total integrated precipitation power in the GUMICS-4
simulation is in quantitative agreement with the observations during quiet
times, i.e., before the two substorm intensifications. We find that during
active times the GUMICS-4 integrated precipitation is a factor of 5 lower
than the observations indicate. However, we also find factor of 2-3
differences in the precipitation power among the three different UVI
processing methods tested here. The findings of this paper are used to
complete an earlier objective, in which the total ionospheric power
deposition in the simulation is forecasted from a mathematical expression,
which is a function of solar wind density, velocity and magnetic field. We
find that during this event, the correlation coefficient between the outcome
of the forecasting expression and the simulation results is 0.83. During the
event, the simulation result on the total ionospheric power deposition agrees
with observations (correlation coefficient 0.8) and the AE index (0.85).
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